- Author: Whitney Brim-DeForest
Whitney Brim-DeForest, UCCE Rice Advisor
We talk about herbicide resistance all of the time in California rice. But how does it evolve in a field? Understanding how herbicide management selects for resistant populations is an important part of preventing the problem from occuring in your fields.
We have many weed species in CA rice that are confirmed to be herbicide resistant. The major herbicide-resistant species are: late watergrass, early watergrass, barnyardgrass, smallflower umbrella sedge, ricefield bulrush (roughseed), sprangletop, and redstem. For this illustration of how herbicide resistance evolves in a field, we use redstem as our example.
Year 1, Beginning of season: A population of redstem is found in a field and are emerging at the beginning of the season. In this illustration, the plants with the blue background are naturally susceptible to an herbicide (Granite SC). The plants with the yellow background are naturally herbicide resistant to Granite SC. There is nothing that the grower has done at thispoint to select for resistance. The genes that make the plant resistant are naturally found in the redstem population in the field.
Year 1, Mid-season: The grower applies Granite SC.
Year 1, End of season: One herbicide resistant plant survives. This plant goes on to produce seed, and the seeds are deposited onto the soil surface, where they are tilled into the soil seedbank at the end of the season.
Year 2, Beginning of season: The redstem population emerges from the soil at the beginning of the season. Because there are more seeds in the soil seedbank from the resistant plants, more of the emerged plants are resistant to Granite SC this year (yellow background = herbicide resistant).
Year 2, Mid-season: The grower again applies Granite SC or another herbicide with the same mode of action (Regiment, Halomax/Sandea or Londax).
Year 2, End of season: All of the herbicide resistant plants again survive the herbicide application. Again, they go on to produce seed, and the seeds are deposited onto the soil surface, where they are tilled into the soil seedbank.
Year 3, Beginning of season: The redstem population emerges from the soil at the beginning of the season. There are even more herbicide resistant plants than the previous 2 years, as the proportion of herbicide resistant seed in the soil has increased.
Year 3, Mid-season: For the third year,the grower applies Granite SC or another herbicide with the same mode of action (Regiment, Halomax/Sandea or Londax).
Year 3, End of season: All of the herbicide resistant plants again survive the herbicide application. Again, they go on to produce seed, and the seeds are deposited onto the soil surface, where they are tilled into the soil seedbank.
Year 4, Beginning of season: The redstem population emerges from the soil at the beginning of the season. This year, all of the plants are herbicide resistant, as the soil seedbank contains mostly herbicide resistant redstem seed.
The illustrations above are an example of how herbicide resistance evolves and is selected for in a field. A grower may not notice during the first year or two, as there are just a few plants that survive the herbicide applications. However, if the grower continues to use the same herbicide year after year, or the same herbicide mode of action, eventually, the population of redstem (or another weed species) will shift to become composed of only plants that are herbicide resistant.
The best way to prevent the development of herbicide resistance is to rotate herbicide modes of action, both between seasons and within seasons. Refer to the UC Herbicide Susceptibility Chart for CA rice when planning an herbicide program.
Optimizing Insect Control and Grain Quality
Wednesday, April 5, 2017
9:00AM - 3:00PM
Lundberg Family Farms
Richvale, CA 95974
We would like to invite you to attend an exciting and informative workshop on insect pest management at rice mills and rice storage facilities. The workshop is organized by the research team of the Post-Harvest Grain Management Project, which was funded by the United States Department of Agriculture, National Institute of Food and Agriculture (Methyl Bromide Transition) Grants Program. The team consists of several scientists with many years experience in the subject of pest management of stored grains in storage and milling facilities.
Major topics covered will include:
1) Current status and challenges of rice grain insect pest management
2) Storage insect pests: identification and monitoring
3) Integrated pest management programs for rice mills and rice storage facilities
4) Structural treatments, residual insecticides, and aeration
5) Economics of rice insect control
6) Decision support systems for pest management
Organizers and Presenters:
Brian Adam, Oklahoma State University
Frank Arthur, USDA-ARS Center for Grain and Animal Health Research
James Campbell, USDA-ARS Center for Grain and Animal Health Research
Luis Espino, University of California Cooperative Extension
Tanja McKay, Arkansas State University
Jim Stewart, Lundberg Family Farms
Mike Stout, Louisiana State University Agricultural Center
Ted Wilson, Texas A&M AgriLife Research
Yubin Yang, Texas A&M AgriLife Research
Register on-line at http://ucanr.edu/2017ricemillworkshop
Registration is free. Please register before April 1st to ensure participation. Seats will be filled on a first-come basis. Lunch will be provided.
****Applied for DPR CE credits****
For more information, contact Luis Espino, University of California Cooperative Extension (530-635-6234, email@example.com) or Jim Stewart, Lundberg Family Farms (530-538-3500)./span>
During our Jan 2017 winter meetings, I conducted a short clicker survey about how bad tadpole shrimp (TPS) has become in the past few years. There were a couple of technical difficulties, and attendees to the Richvale meeting didn't get to see the answer to the questions. I thought it would be a good idea to share the results of the survey here. The results were very similar for all meetings, so I have aggregated all the answers.
Q1: In your opinion, compared to 10-15 years ago, TPS problems are currently:
Total respondents: 109
About half of respondents thought TPS problems are the same than 10-15 years ago and almost 40% thought problems were somewhat or much worse. This seems to indicate that TPS problems are slowly becoming worse. It might have to do with the fact that copper sulfate is more expensive, less effective against algae, and therefore less used; and pyrethroids don't seem to be working as well as before (see question 2).
Q2: Have you noticed a reduction in the efficacy of pyrethroid insecticides controlling TPS?
Total respondents: 119
A third of respondents have noticed a reduction in pyrethroid efficacy for TPS control. This is alarming. Last year, TPS from two fields were confirmed as tolerant to pyrethroids. Responses to this question indicate that there might be way more fields with tolerant TPS out there.
Q3: If you treat for TPS, do you:
Total respondents: 90
A bit over half of respondents scout their fields before doing a TPS treatment (wait), and 40% schedule treatments. In my opinion, both approaches are valid. TPS develops very fast, specially in late planted fields, and in problem fields, they will show up no matter what.
Responses to the questions indicate that we need new alternatives for TPS control and tools to make scouting easier. Some of the work being done to address these questions was presented during our last winter meetings. The presentation is posted on-line on the UC Rice On-line website.
The University of California Cooperative Extension annual rice meetings will be held this week. As usual, we will have four locations. However, note the change of venue for the Glenn and Colusa meetings this year. This year these meetings will be at the Glenn County Office of Education in Willows, and the Colusa Casino Conference Center in Colusa. The Richvale and Yuba City meetings will be held at their usual locations.
WHERE & WHEN
Richvale: Thursday, Jan. 26, 8:30 am, Evangelical Church, 5219 Church St., Richvale
Glenn: Thursday, Jan. 26, 1:30 pm, Glenn County Office of Education, 311 South Villa Avenue, Willows
Colusa: Friday, Jan. 27, 8:30 am, Colusa Casino Resort, 3770 Hwy 45, Colusa
Yuba City: Friday, Jan. 27, 1:30 pm, Veterans Hall, 1425 Veterans Memorial Circle, Yuba City
TIME: Doors open at 8:00 am and meetings start at 8:30 am at Richvale and Colusa. Doors open at 1:00 pm and meetings start at 1:30 pm at Glenn and Yuba City.
8:00 a.m. (1:00 p.m.) Doors open, sign-in, coffee
8:30 a.m. (1:30 p.m.) Call meeting to order - Rice Research Board Nominations – Dana Dickey, Rice Research Board
8:35 a.m. (1:35 p.m.) Rice Pesticide and Regulatory Update – County Ag Commissioner
8:50 a.m. (1:50 p.m.) Weedy Rice in California – Whitney Brim-DeForest, UCCE
9:20 a.m. (2:20 p.m.) New Rice Seed Policy for RES Varieties – Kent McKenzie, RES
9:40 a.m. (2:40 p.m.) Arthropod Management Update – Luis Espino, UCCE
10:00 a.m. (3:00 p.m.) Fertility Update – Bruce Linquist, UCCE
10:30 a.m. (3:30 p.m.) Weed Management Update – Kassim Al-Khatib, UCCE
11:00 a.m. (4:00 p.m.) — ADJOURN —
- Author: Whitney Brim-DeForest
In the past year, the California rice industry has begun to deal with a new pest: “weedy rice”, also known as “red rice”. Weedy rice is a common weed in rice-growing regions of the world, and when infestations are high, it can significantly reduce yields. In the southern USA, losses have been as high as 60% when uncontrolled. In 2016, through the efforts and cooperation of rice growers and Pest Control Advisors, weedy rice has been identified on over 10,000 acres in Butte, Glenn, Colusa, Sutter, Yuba, Placer and Yolo counties. Although 10,000 acres may sound like a lot, it is still only a small percentage of the total rice acreage in California (about 2%).
What makes "weedy rice" unique is that it is the same species as domesticated rice (both are Oryza sativa L.). This means that growers can only control weedy rice through non-chemical means, since any herbicides applied to control the weedy rice will also kill the crop. In the California rice cropping system, where chemicals are the primary method of weed control, growers can use cultural practices such as as a stale seedbed before the rice season. However, this can delay planting by as much as a month. Alternatively, growers can fallow or rotate with another crop, and if the infestations is high, this may be the best option. During the growing season, if weedy rice is found in the field, the only option that growers currently have is to hand-pull it out.
How does a grower know if they have weedy rice? Weedy rice can be identified before flowering, when all grass-control herbicides have been applied:
- If grassy weeds remain in the field, check for an auricle and ligule (see photo below).
- If none are present, then the grassy weed is likely a watergrass species.
- If an auricle and ligule are present, it may be weedy rice, and it is time to get help with identification. A PCA or UCCE Rice Advisor should be able to assist in identification.
Once rice has headed (produced seed), weedy rice panicles and the panicle of the crop will look similar, so growers should look for any that are different than the planted variety. Again, a PCA or UCCE Rice Advisor can assist in identification. If the field is a certified seed field, then the California Crop Improvement Association (CCIA) should be called to identify the suspect plants.
Many growers have asked why it is important to control weedy rice, since weedy rice is still rice, and therefore, edible. There are a number of ways that weedy rice can impact rice production:
1) Reducing milling quality: Due to the extra milling required to remove the red-colored bran, the number of cracked and broken kernels will increase, therefore decreasing the value and the price paid to the rice grower. If the rice is to be milled and sold as brown rice, large amounts of red bran can reduce the milling yield significantly.
2) Hybridization with domesticated varieties: Weedy rice can cross with domesticated varieties in the field. If there is a high number of weedy plants in a field, the odds that this will occur is even greater. The hybrids (between weedy rice and domesticated varieties) may have different characteristic than their parents (more vigorous growth, for example).
3) Yield decreases: Since weedy rice shatters (falls off of the panicle before harvest), once the population reaches a critical threshold in the field, yields can decrease significantly.
4) Weed management cost: Weedy rice cannot be managed by chemical means. Therefore, any control efforts have to be through cultural practices. One of the most effective methods is to hand-pull it out of the field. Labor, as we all know, is very expensive.
Weedy rice is a manageable pest in California rice, but it will only be possible through the joint efforts of rice growers, PCA's and members of the rice industry. It will take accurate identification in the field, as well as timely and sustained control efforts in the field.